Preparation of metal-organic frameworks of different net topologies via conventional solvothermal reactions and via the combination of solvothermal reactions and postsynthetic modifications

Abstract

[Part A] Metal-organic frameworks (MOFs), [(MnⅡ3O)L3S3] (1) and [(MnⅡ5O2)L4S8] (2), were prepared using a new ligand, 2,6-di(1H-tetrazol-5-yl)naphthalene (2,6-H2NDT), in which two tetrazole units are connected via the naphthalene group. The ligands in HNDT-1/NDT2- deprotonation states offer a very rich coordination chemistry as a result of having two tetrazolate rings, each with three/four possible donor nitrogen atoms and may supply diverse coordination modes. The single crystal diffraction study reveals that 1 is constructed from a trinuclear {MnⅡ3} building-block as a 6-connected secondary building unit (SBU) and the ligand in HNDT-1 and NDT2- deprotonation states as a linker. It shows that the tetrazolate groups adopt a bidentate (1,2-μ bridging) binding mode with the MnⅡ centers in 1. The trinuclear SBU is connected to six neighboring SBUs, which can be considered a six-connected node, to form the 3D MOF of an acs net topology, 1. 2 is constructed from a pentanuclear {MnⅡ5} building-block as a SBU and the ligand in HNDT-1 and NDT2- deprotonation states. It shows that the tetrazolate groups adopt a monodentate binding mode, bidentate (1,2-μ and 2,3-μ bridging) binding modes, and a tridentate binding mode with the MnⅡ centers in 2. The pentanuclear SBU is connected to eight neighboring SBUs, which can be considered an eight-connected node, to form the 3D MOF of a bcu net topology, 2. The structural characteristics and sorption behaviors of the two MOFs of different net topologies will be discussed in the paper.|[Part B. Section 1] The preparations of the two isoreticular MOFs, Ni(HBTC)(dabco)] (2) and [Ni2(HBTC)2(bipy)0.6(dabco)1.4] (3) (where, H3BTC = 1,3,5-benzenetricarboxylic acid; dabco = 1,4-diazabicyclo[2.2.2]octane; and bipy = 4,4’-bipyridine), were demonstrated via the postsynthetic ligand exchange of [Ni(HBTC)(bipy)] (1). By soaking 1 in a high concentration of dabco DMF solution, all of the aromatic bipy pillaring linkers in 1 were completely exchanged by the shorter aliphatic dabco pillaring linkers to form the isoreticular MOF, 2, with reduced pore dimension and volume. In contrast, the soaking of 1 in a low concentration of dabco DMF solution led to the MOF, 3, with the partially and selectively exchanged additional component, dabco linker. Controlling the concentration of dabco, not only 2 with completely exchanged dabco but also 3 with selectively exchanged dabco in the alternating layers could be obtained. The structural characteristics, PXRD patterns and sorption behaviors of the three MOFs will be discussed in the presentation.|[Part B. Section 2] The metal-organic frameworks (MOFs), [Ni(HBTC)(pz)] (3) (hms net topology) (where, H3BTC = 1,3,4-benzenetricarboxylicacid; pz = pyrazine) and [Ni(HBTC)(bipy)] (4) (gra net topology) (where, bipy = 4,4’-bipyridine) that were unattainable via conventional synthetic approach, were prepared via the postsynthetic ligand exchanges of 3-D MOFs, [Ni(HBTC)(bipy)] (1) (hms net topology) and [Ni(HBTC)(pz)] (2) (gra net topology), respectively. The MOFs, [Ni(HBTC)(pz)] (5) (gra net topology) and [Ni(HBTC)(bipy)] (6) (gra net topology) that are the same as 2 and 4, respectively, were prepared via the postsynthetic ligand insertions into 2-D MOF [Ni(HBTC)(DMF)] (hcb net topology). 1 and 4 (or 6) are the polymorphic MOFs of the same 3,5-connected but of different net topologies, hms and gra net topologies, respectively, with the same [Ni(HBTC)(bipy)] formula. 2 (or 5) and 3 are also the polymorphic MOFs of the same formula unit, [Ni(HBTC)(pz)]. 1 and 3 are the isoreticular structures of the same hms net topology and 2 and 5 also are the isoreticular structures of the same gra net topology.